How to select and scale same time
Selecting just the outer edges doesn't work in this case, this is how I would do it:

In Edit Mode use Face Select, select all the inner faces of those grooves.
Make sure you have set the Transform Pivot Point set to Individual Origins.
Hit S and then Z to scale them on the Z axis as far as you want the outer edges to be.
Then hit Ctrl+Numpad Minus to reduce the selection of the inner faces.
Scale them back again on the Z axis with S and Z.